Along the lines of Alexei
x = A*Exp[I*phi]
A*E^(I*phi)
(* the next step effectively removes A ; does not work with A < 0 *)
FullSimplify[Arg[x], A > 0]
Arg[E^(I*phi)]
(* now ComplexExpand dos the rest *)
y = ComplexExpand[%]
ArcTan[Cos[phi], Sin[phi]]
Wolfgang
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"Ben" <bjgear at googlemail.com> schrieb im Newsbeitrag
news:j73grj$fvk$1 at smc.vnet.net...
> Would appreciate any help here, endless Googling has not revealed the
> answer to me:
>
> If I define a complex number symbolically, such as x = A Exp[I phi],
> why does Arg[x] never return the answer I expect, phi? Using Refine
> with the as sumptions phi is real and between 0 and 2 pi, and that A
> is greater than 0 doesn't seem to help. All I get is Arg[Exp[I phi]]
>